class Animal(object):
    def speak(self):
        print("动物的叫声")
        pass

class Cat(Animal):
    def speak(self):
        print('喵喵')

class Dog(Animal):
    def speak(self):
        print('汪汪')

class Test(object):
    def speak(self):
        print('test')

def speak(object): # Animal
    object.speak()

animal = Animal()
# animal.speak()

kitty = Cat()
puppy = Dog()
# kitty.speak()
# puppy.speak()

speak(animal)
speak(puppy)
speak(kitty)

t = Test()
speak(t)
